1. Field of the Invention
The present invention relates to an optical information reader for reading optical information from/a read object on which such optical information as a bar code or the like is printed or recorded.
2. Description of Related Art
Conventionally, as an optical information reader of this kind, as shown in FIG. 25, a bar-code reader 90 is well known in which a light source 83, a lens 86, an image sensor (hereinafter called as a line sensor) 87, a trigger switch 88 and an electronic circuit board 89 are assembled integrally into a hand-held housing 80. The light source 83 is constructed to array in line plural light emission diodes for irradiating light to a bar-code label 82 on which a bar code 81 is printed. The lens 86 converges reflected light from the bar-code label 82 through a mirror 84 and a stop or an iris diaphragm 85 to focus an image of the bar-code label 82 on a rear portion. The line sensor 87 is arranged at a focusing position of the lens 86 and constructed by arraying charge coupled-elements in line for converting the image of the bar-code label 82 into an electric signal. The trigger switch 88 inputs reading instruction of the bar code 81 with manual operation. The electronic circuit board 89 is connected to the light source 83, line sensor 87 and trigger switch 88.
As shown in FIG. 26, on the electronic circuit board 89, an amplifier 91, a binarizing circuit 92, a count part 93, a decode part 95, a control part 96, a power source 97 and the like are mounted. The amplifier 91 amplifies a feeble analog image signal outputted by the line sensor 87. The binarizing circuit 92 binarizes the analog image signal amplified by the amplifier 91 to convert the binarized signal into a digital signal. The count part 93 counts a width of the digital signal outputted by the binarizing circuit 92 to measure widths of bars and spaces of the bar code 81. The decode part 95 decodes the bar code 81 on a basis of an output signal from the count part 93 and outputs the decoded result to an external circuit through an external terminal 94. When reading instruction of the bar code 81 is inputted by actuation of the trigger switch 88, the control part 96 causes the light source 83 to be driven so as to irradiate the bar code 82 and also causes the count part 93 and decode part 95 to operate so as to output the decoded result of the bar code 81 at the external terminal. In addition, generally, the count part 93, decode part 95 and control part 96 are realized by a microcomputer (ECU) which comprises CPU, ROM, RAM and the like.
However, such a conventional bar code reader is a so-called touch type bar code reader which reads the bar code 81 in contact with a read opening 80a of the housing 80 providing a passage of the irradiated light and reflected light with the bar-code label 82. Thus, it becomes difficult to correctly read the bar code 81 when the read opening 80a is separated or kept apart from the bar-code label 82.
Namely, when the read opening 80a contacts the bar-code label 82 in such a conventional bar-code reader, an optical path length of light reaching the line sensor 87 from the light source 83 through the bar-code label 82 is maintained constant. Moreover, there is very little external light entering into the optical path in the housing 80. Thus, intensity of reflected light entering into the line sensor 87 is varied only substantially according to the bar code 81.
When the read opening 80a is separated from the bar-code label 82, however, the optical path of light reaching the line sensor 87 from the light source 83 becomes long. Moreover, the external light enters into the optical path. Therefore, intensity of reflected light entering into the line sensor 87 changes largely according to attenuation of the irradiated light and increase of reflected light caused by external light on the optical path. Thus, in the conventional bar-code reader, a quantity of reflected light to be converted into an electric signal by the line sensor 87 is too much or too little. As the result, it becomes difficult to correctly read the bar code 81.
In the conventional bar-code reader, as described above, it is necessary to contact the read opening 80a with the bar-code label 82. There is, therefore, also a problem that a bar code having a total width which is more than an opening diameter W of the read opening 80a may not be read.